Since I have hooked up a VT220 instead of my VT320 I have a strange
problem, I would like some advice as to whether this is related to the
terminal setup or to NetBSD.

The display gets corrupted by reversed question marks at random points
in the text.  This happens both during the boot process and during
normal use.  The terminal is set up as English with a North American
keyboard.  The comms set up is correct for the MicroVAX 3100 to which it
is attached.
-- 
Regards
Pete